#!/bin/bash

#
# Bash script to automatically control the backlight brightness using the illumination sensor
# Written because the Gnome 45.4 auto brightness is not smooth unlike my previous MacOS laptop
# which was driving me insane.
#
# Features:
#  * smooth, flicker-free ramping
#  * sensitivity and delay to prevent constant adjustments
#  * manual adjustment though backlight keys or software(*)
#  * should work on all Framework 13 AMD and Intel laptops (**)
#
#  (*) manual adjustment can be a bit glitchy at times
#  (**) Intel has not yet been tested
#
#  Adapted from script by Michiel Toneman
#  Released under the Apache License V2.0

# Define the appropriate devices for Intel and AMD systems
if [ -f /sys/class/backlight/intel_backlight/brightness ]
then
  screen_brightness=/sys/class/backlight/intel_backlight/brightness
  screen_actual_brightness=/sys/class/backlight/intel_backlight/brightness
  screen_max_brightness=/sys/class/backlight/intel_backlight/max_brightness
else
  screen_brightness=/sys/class/backlight/amdgpu_bl1/brightness
  screen_actual_brightness=/sys/class/backlight/amdgpu_bl1/actual_brightness
  screen_max_brightness=/sys/class/backlight/amdgpu_bl1/max_brightness
fi

# Set some constants
max=$(cat $screen_max_brightness)
sensitivity=$((max/20))
min=1
delay=1 # Check every 5 seconds
debug=0 # Set to 1 for debug output

# Variables
manual_adjust=0 # Start with manual adjustment set to 0
last_target=$(cat $screen_actual_brightness) # Start the target brightness at the current screen brightness
declare -i target=96000

# Loop
while [ 1 ]
do
    doupdate=0

    # Get the current state of the backlight and illuminance sensor
    sensor=$(cat /sys/bus/iio/devices/iio:device0/in_illuminance_raw)
    if [ $debug -eq 1 ]
      then
      echo "Got sensor as $sensor"
    fi
    backlight=$(cat $screen_actual_brightness)

    # If the backlight has been manually changed since the last
    # change by the script, we take the delta and add it to the manual
    # adjustment.
    # Reset the manual adjustment by manually dimming to minimum
    if [ $((backlight - last_target)) -ne 0 ]
    then
      if [ $backlight -lt 4 ] # Backlight controls don't appear to go below 2
      then
        manual_adjust=0
      else
        #manual_adjust=$((manual_adjust + (backlight - last_target)))
        last_target=$backlight
      fi
    fi

    # The target brightness is the sensor reading plus the user's (positive or negative) adjustment
    #target=$(( (sensor / 3355 * 96000) + manual_adjust ))
    target=$(( sensor * 960 ))
    if [ $debug -eq 1 ]
      then
      echo "Calculated target as $target"
    fi

    # Check if delta between ambient and current backlight exceeds the sensitivity threshold
    # so that we don't keep changing brightness all the time
    if [ $backlight -gt $target ]
    then
        if [ $((backlight - target)) -gt $sensitivity ]
        then
          doupdate=1
        fi
    fi
    if [ $backlight -lt $target ]
    then
        if [ $((backlight - target)) -lt $sensitivity ]
        then
          doupdate=1
        fi
    fi

    # Check that we don't exceed the min and max brightness values
    if [ $target -gt $max ]
    then
      if [ $debug -eq 1 ]
        then
        echo "Adjusting target to max value"
      fi
      target=$max
    fi
    if [ $target -lt $min ]
    then
      if [ $debug -eq 1 ]
        then
        echo "Adjusting target to min value"
      fi
      target=$min
    fi

    if [ $doupdate -eq 1 ]
    then
      # Debug logging
      if [ $debug -eq 1 ]
        then
        echo “Starting brightness: $backlight”
        echo “Ambient light: $sensor”
        echo “Manual adjustment: $manual_adjust”
        echo “Target brightness: $target”
        echo “-------------------------------”
        echo “Sensitivity: $sensitivity”
        echo “Min: $min Max: $max”
        echo
      fi

      # Now change the brightness smoothly in single value in/decrements per 20ms
      intermediate=$backlight

      if [ $debug -eq 1 ]
        then
        echo "Entering while loop ..."
      fi
      #while [ $intermediate -ne $target ]
      diff=$(($intermediate - $target))
      if [ $debug -eq 1 ]
        then
        echo "Diff is $diff"
      fi
      diff_abs=$(( $diff * (($diff>0) - ($diff<0)) ))
      if [ $debug -eq 1 ]
        then
        echo "Diff Abs is $diff_abs"
      fi

      while [ $diff_abs -gt $sensitivity ]
      do
        if [ $intermediate -lt $target ]
        then
          #((intermediate++))
          #intermediate=($intermediate + 1000)
          intermediate=$((intermediate + $diff_abs/80))
        else
          #((intermediate--))
          #intermediate=($intermediate - 1000)
          intermediate=$((intermediate - $diff_abs/80))
        fi
        if [ $debug -eq 1 ]
          then
          echo "Setting s_b to $intermediate"
        fi
        echo $intermediate > $screen_brightness
        #screen_brightness=$intermediate
        sleep 0.01
        if [ $debug -eq 1 ]
          then
          echo "Re-checking target..."
        fi
        target=$(( $(cat /sys/bus/iio/devices/iio:device0/in_illuminance_raw)  * 960  ))
        # Check that we don't exceed the min and max brightness
        if [ $target -gt $max ]
          then
          if [ $debug -eq 1 ]
            then
            echo "Adjusting target to max value"
          fi
          target=$max
        fi
        if [ $target -lt $min ]
          then
          if [ $debug -eq 1 ]
            then
            echo "Adjusting target to min value"
          fi
          target=$min
        fi
        diff=$(($intermediate - $target))
        if [ $debug -eq 1 ]
          then
          echo "Diff is $diff"
        fi
        diff_abs=$(( $diff * (($diff>0) - ($diff<0)) ))
        if [ $debug -eq 1 ]
          then
          echo "Diff Abs is $diff_abs"
        fi
      done
      if [ $debug -eq 1 ]
        then
        echo "Ended while loop!"
      fi

      # Remember what the target brightness was
      # If the next time round the last target brightness differs from the current backlight value
      # then the assumption is that someone has manually adjusted the brightness and we can use that delta
      last_target=$target
    fi
  if [ $debug -eq 1 ]
    then
    echo "Loop end, sleeping $delay"
  fi
  sleep $delay
done